Intermittent Claudication and Muscle Fiber Fine Structure: Morphometric Data on Mitochondrial Volumes

Abstract

The mitochondrial volume densities (V mit) of the different fiber types (type 1, type 2A, type 2B) were estimated in bilaterally obtained biopsies from 22 patients with unilateral intermittent claudication. These data, which were obtained from structurally intact fibers, were compared with clinical data from the same subject In both the asymptomatic and symptomatic legs, V mit 1 > V mit 2A > V mit 2B. Furthermore, V mit 1 covariated with Vmit 2A and V mit 2A with V mit 2B in the asymptomatic legs (as in healthy subjects) but not in the symptomatic legs. V mit 2 (mainly Vmit 2A) covariated with the age of the subjects in both legs. V mit Tot was higher in the symptomatic legs than in the asymptomatic legs. This was mainly due to increase in the oxidative fibers, type 1 and type 2A. Usually, V mit in the asymptomatic legs covariated sig-nificantly with the results of the functional tests (initial pain and maximum walking tolerance), while only V mit 2A in the symptomatic legs showed such a corre lation. However, the difference between the two legs concerning V mit 1 was also correlated to the walking tolerance. Patients with high stenosis or occlusion showed higher Vmit Tot than did those with low obstacles. The results conclusively show that a fiber type-specific adaptation to ischemia occurs through an increase of mitochondrial content of oxidative fibers, which suggests that hypoxia may influence the control of synthesis or degradation of mitochondrial proteins.

Key Words:

• human muscle fiber
• ultrastructure
• mitochondria
• stereology
• ischemia
• age